Considerable interest has recently been focused on the problem of limiting the mass of particulate matter emitted with the exhaust gases from diesel and other internal combustion engines. In the case of diesel engines, a great deal of effort is currently being expended to develop practical and efficient devices and methods for reducing emissions of largely carbonaceous particulates in exhaust gases.
One method for accomplishing this is to provide a suitable particulate trap having at least one particulate filter therein in the exhaust system of a diesel engine with this filter being capable of efficiently trapping the particulates from the exhaust gases and also being adapted to be regenerated, as for example, by the in-place incineration of the trapped particulates.
One suitable particulate filter is a ceramic wall-flow monolith filter of the type as disclosed, for example, in U.S. Pat. No. 4,276,071 entitled Ceramic Filters for Diesel Exhaust Particulates issued June 30, 1981 to Robert J. Outland. Such a particulate filter is originally in the form of an extruded ceramic monolith having an outer wall interconnected by a large number of interlaced thin porous internal walls defining a plurality of substantially parallel cells. A first group of alternate cells are closed, as by a plug of cement material, at one end, while a second group of such cells are closed in a similar manner at the opposite end whereby to define inlet and outlet passages, respectively.
Due to the method of manufacture of the monolith which is first extruded and then fired, the matrix of cells in the extrusion, after being fired, are not dimensionally the same from monolith to monolith making multiple cell plugging difficult. Accordingly, and as disclosed in the above-identified U.S. Pat. No. 4,276,071, the plug of cement material has been applied one cell at a time as by means of a hypodermic needle-like plunger.